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Text-based UML diagram description format used by PlantUML.
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The .puml file format is a plain text format used to define UML diagrams through scripting. These files are primarily associated with the PlantUML tool, which generates UML diagrams from textual descriptions.
Users create and edit .puml files using simple text editors, and they can be visualized or exported using PlantUML software or compatible tools. This format simplifies diagram creation, version control, and automation in software development workflows.
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Date updated: June 15, 2026
.puml files contain textual descriptions of UML diagrams, including class, sequence, and activity diagrams, among others. The syntax is straightforward and allows users to define relationships, classes, actors, and other UML components with concise commands.
The format was popularized by PlantUML, an open-source tool that converts these textual descriptions into visual diagrams and supports multiple output formats, including PNG, SVG, and LaTeX. The .puml format has become a standard for documentation, automation, and version-controlled diagram creation in agile development processes.
The structure of a .puml file involves defining diagram types, specifying diagram elements, and relating them through syntax that is easy to learn and extend. It is cross-platform, working on Windows, Mac, and Linux, with PlantUML support and compatible integrations in IDEs like Visual Studio Code, IntelliJ IDEA, and more.
This format supports macro definitions, skinparams for styling, and directives for modular diagram construction, making it flexible and powerful for a range of UML modeling needs.
To open and view .puml files, the most common tool is PlantUML. You can use the command-line version on Windows, Mac, or Linux, or integrate it within IDEs such as Visual Studio Code, IntelliJ IDEA, or Eclipse via plugins. Most of these tools allow you to generate diagrams directly from the .puml file or preview them interactively.
Additionally, online editors and viewers like the official PlantUML website or third-party web services support uploading or pasting the code to visualize diagrams without installing any software. Desktop applications and plugin integrations are also widely available for seamless editing and rendering.
Converting .puml files typically involves exporting the UML diagrams generated by PlantUML into images or other formats such as SVG or PDF. Most tools that open .puml files support exporting directly from their interface. You can also use command-line options with PlantUML to batch convert multiple files to various image formats.
For online conversions, several web services allow uploading a .puml file and downloading the diagram in different formats. If you need to integrate this into automated workflows, scripting with PlantUML commands or using APIs from diagram conversion tools can streamline the process.
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